How To Select an Intrinsically Safe Pressure Transducer

1. Be assured that the pressure transducer has been significantly modified for intrinsically safe applications — the printed circuit board has been simplified to use low voltage and current, capacitors and inductors have been minimized, etc. Intrinsically safe pressure transducers typically operate on low voltage DC (VDC) and consume less than 1 watt of power. If a capacitance type pressure transducer is desired for an application, it also can be certified as intrinsically safe.

2. Be sure to select small sputtered thin film units, that are less than 1" in diameter, and made of all stainless steel wetted parts. They should come with a broad selection of electrical and pressure connections, and a wide choice of electrical outputs ready for installation. Heavy-duty applications will feature a thicker diaphragm and a pressure resistor designed to withstand the rigors of cavitation and extreme pressure spikes.

3. State-of-the-art intrinsically safe pressure transducers use the well-proven Wheatstone bridge principle. Molecular layers are sputtered onto a 17-4 PH stainless steel diaphragm and the circuit is etched to provide excellent resistor definition and uniformity. Sputtered thin film technology allows the design of simple, highly accurate and compact strain gauges deposited onto the back of the sensing diaphragm, which is in direct contact with the media. Find a design that provides ±0.25 percent full-scale accuracy over its full temperature range. In addition, it should have long-term stability of better than ±0.1 percent full scale per year, enhanced sensitivity, and virtually no drift.

4. Construction should be all welded stainless steel with no internal elastomers, RTV silicon adhesive sealant or epoxies. The unit should offer a wide pressure range, such as from 75 PSI to 32,000 PSI. It should have no oil that could cause thermal instability and/or leakage. Verify the unit is CE and RoHS compliant.

5. Engineers may consider using a capacitance based pressure transducer design to minimize orientation and vibration issues by using a stretched stainless steel diaphragm that is not fluid filled. The only gravity effect it has is the weight of the diaphragm, which is not insignificant, but very small and is easily compensated for in the field.